You can create selections in more than one channel at a time.
Open the Selection tab on the left of the sound window.
Check boxes next to channels in which you want cloned selections to appear.
Cloned versions of a selection drawn in one of these channels will appear in the others.

You can also add a cloned version of an active selection to another channel.
Do this by first activating the selection.
Then, in the Selection tab on the left of the sound window, check the boxes of the channels in which you want the selection to appear.

Another way to do specify identical start/end times and frequency bounds for selections:
After saving a Selection table,
you can open it in a spreadsheet program (like Excel for instance) and add begin time, end time, low frequency, and high frequency values into the table.
Next, save this modified table as a text file
--> be certain that you do *not* alter the column headings of the first seven columns. (Otherwise Raven will not be able to recognize it as a Selection table)
Then, in Raven, you can open the modified table with its corresponding sound file, and the selections will appear.